laughing on the outside, crying on the inside
An acronym designed for when either: 1- Something is superficially very amusing but actually quite depressing; or 2- Someone finds something which would ordinarily be quite tragic to be unreasonably amusing and wants to give the impression that they aren't totally soulless.

1. Jack: Well I would've rogered your mum, but I didn't want to get aids!
Jill: Damn,... lotocoti... (Jill actually has AIDS)

2. Jill: So last weekend I was skydiving with my bff Jan, and her chute didn't open!